1. Field of the Invention
The present invention relates to an improvement of a high pressure fuel pumping apparatus, and more particularly to a high pressure pumping apparatus used for an in-cylinder jet gasoline engine.
2. Description of the Related Art
Referring to FIG. 6, an explanation will be given of a related high pressure fuel pumping apparatus.
In FIG. 6, reference numeral 1 denotes a fuel jet valve for directly jetting fuel into each of cylinders of an engine (not shown). Reference numeral 2 denotes a delivery pipe for supplying fuel to the fuel jet valve. Reference numeral 3 denotes a high pressure fuel pumping apparatus for supplying the high pressure fuel into the delivery pipe 2 through a high pressure fuel supply passage 4. Reference numeral 5 denotes a high pressure fuel pump of a piston type. Reference numeral 6 denotes an inhalation valve for the high pressure fuel pump, which is constructed from a lead valve. Reference numeral 7 denotes a discharge valve for the high pressure fuel pump, which is constructed from a lead valve. Reference numeral 8 denotes a high pressure fuel regulator for regulating the fuel pressure of fuel discharged from the high pressure fuel pump 5 at a prescribed value. Reference numeral 9 denotes a high pressure damper mounted between the high pressure fuel regulator 8 and the high pressure fuel pump 5. Reference numeral 10 denotes a low pressure fuel passage which is connected to a low pressure fuel pump (not shown). Reference numeral 11 denotes a low pressure damper. Reference numeral 12 denotes a drain passage for returning the fuel having leaked from a gap between the sleeve and piston of the high pressure fuel pump 5 toward a fuel tank. Reference numeral 13 denotes a drain passage for the high pressure fuel regulator 8. Reference numeral 14 denotes emerging point of the drain passages 12 and 13. Reference numeral 15 denotes a returning passage which is communicated with the fuel tank (not shown) Reference numeral 16 denotes a check valve which is arranged on the drain passage 12 for the high pressure fuel pump 5, which is constructed from a ball valve.
In the related pumping apparatus having a structure described above, the check valve 16 is arranged in the drain passage 12 for the high pressure fuel pump 5, and the amount of the fuel which has leaked from a gap between the sleeve and piston of the high pressure fuel pump 5 stands within a high pressure fuel drain chamber, thereby preventing the pressure of the drain chamber from being boosted and a fuel sealing metallic bellows from being broken.
The check valve 16 of the related apparatus serves to prevent the fuel in the drain passage 13 for the high pressure fuel regulator 8 from flowing backward into the drain chamber of the high pressure fuel pump 5.
The check valve 16 of the related pumping apparatus serves to discharge the fuel standing within the drain chamber of the high pressure fuel pump 5 and to prevent the fuel in the drain passage 13 for the high pressure fuel regulator 8 from flowing backward into the drain chamber of the high pressure fuel pump 5.
However, the above check valve 16, which is constructed from a ball valve, provides poor response property for the high pressure fuel pump. Therefore, the fuel stands too much within the drain chamber of the high pressure fuel pump 5, so that the internal pressure of the drain chamber increases. This will deteriorate the endurance of the fuel sealing metallic bellows constructing the inside of the drain chamber.